Marine Corps traditional concepts of readiness and fast, effective deployment were never better illustrated than in the hectic weeks following 25 June 1950. The NKPA invasion of South Korea came at a time when U.S. military forces were in the final stages of a cutback to peacetime size. Ships and planes were being “mothballed”; personnel of all the Armed Services were being reduced in number to the lowest possible effective manpower levels.
From the peak of its six-division, five-wing wartime strength of 475,600 in 1944–1945, the Marine Corps at the outbreak of the Korean emergency had only two skeletal divisions and two air wings. There were but 74,279 Marines on active duty, 97 percent of the Marine Corps authorized strength. Although a ceiling of 100,000 had been established for the Corps by law, it was a period of tight purse strings for all defense components. Fiscal austerity in the post-World War II period had whittled Corps numbers from 85,000 in FY 1947 to what was projected at 67,000 by the end of FY 1950.
This critically reduced strength found the normal Marine triangular infantry organization cut back to two companies per battalion, two battalions per regiment, and two regiments per division. The 1st Marine Division, at Camp Pendleton, and 2d Marine Division, at Camp Lejeune, were structured along the regular peacetime T/O of 10,232 USMC/USN vice the wartime minimum T/O of 22,355. No Marine units of any size were located in the Far East.
Despite its lean numbers in late June 1950, the Marine Corps once again would be in the forefront of American military response to the Communist aggression 6,000 miles across the Pacific. As hard-pressed South Korean forces and understrength U.S. occupation troops from Japan attempted to halt the Communist invaders, General of the Army Douglas MacArthur, on 2 July, requested the JCS to send immediately a Marine RCT with supporting air to the Far East. On 7 July, the 1st Provisional Marine Brigade was formed at Camp Pendleton from units of the 1st Division. Major components of the brigade—a balanced force of ground, service, and aviation elements—were the 5th Marines and MAG-33. Five days later, the 6,534-man brigade had mounted out from San Diego to answer the CinCFE plea for Marines to help turn the Communist tide engulfing Korea.
The brigade buttressed the faltering UNC defense in the Pusan Perimeter. Employed as a mobile reserve it helped prevent three enemy breakthroughs—at Chinju and the two Naktong River battles. On 7 August, a month after its activation, the brigade launched an attack toward Chinju. The Marine brigade was the first unit sent from CONUS to see combat in what was then considered a short-term police action. Later, in leading the way to destruction of an enemy bridgehead at the Naktong, the Marine brigade gave the defending Eighth Army its first victory against the NKPA in the Korean conflict.
Even before the brigade had been dispatched to the Far East, as the Korean situation continued to deteriorate, MacArthur had requested the JCS to expand the brigade to a full war-strength division. Between 10–21 July MacArthur, now CinCUNC, had made three separate requests for a Marine division. This persistence was reinforced by his growing determination to conduct a tactical amphibious operation to the rear of the overextended NKPA lines and thereby seize the initiative from the enemy.
In the States, meanwhile, authorization was received to bring the badly understrength 1st and 2d Marine Divisions up to full 22,000-man war levels. By stripping posts and stations, reassignment and rerouting of units, and callup of additional reserve personnel, major elements of the 1st Marine Division were on their way to Korea by mid-August. Timing was critical in order to meet the projected D-Day target date of 15 September.
Pulled out of the Pusan line on 12 September, the brigade was absorbed by the newly arrived 1st Marine Division in preparation for the coming Inchon invasion. As the brigade commander, Lieutenant General Edward A. Craig, USMC, later reminisced:
Although the 1st Provisional Brigade and the 1st MarDiv had never actually trained or worked together, they still combined and executed a successful landing. To me, this simply emphasized the fine training and techniques laid down for amphibious landings by the Marines.[692]
[692] CheVron, pp. 4–5.